1. Field of the Invention
This invention relates to apparatus for inflicting standard puncture wounds in the skin for medical diagnosis. Many medical procedures such as those for the diagnosis of disturbances of hemostasis and blood coagulation and the like require the artificial creation of a small standard wound of a known size with great accuracy in order to obtain reproducible results. A common procedure of this sort is the determination of bleeding time. A new procedure was recently developed at the Mayo Clinic in Rochester, Minnesota, to automatically determine the pattern of bleeding. This invention particularly relates to lancet holders, also called "spring lancets" of the type used to create artificial, standard wounds in the earlobe or fingertip or other skin surface of a highly accurate and consistent size.
2. Description of the Prior Art
The conventional lancet holder provides a lancet or blade that is guided in a tube which is placed upon the spot where the wound is to be created. Upon actuation of a trigger mechanism, the lancet is hurled from the tube and thus inflicts a wound whose depth and/or size may be only very coarsely controlled. In order to prevent infection, disposable lancets are sometimes utilized. One difficulty with such devices with regard to the reproducibility of the size of the wound is that the lancet is removed from the skin when the lancet holder is drawn away from the surface of the skin by the medical technician. The skill of the technician therefore greatly affects the accuracy of the size of the standard wound created by the lancet.
An improvement on the conventional lancet holder is known in which the lancet is automatically drawn out of the wound after puncture. This device is described in the article by A. H. Sutor, E. J. Bowie, J. H. Thompson, Jr., P. Didisheim, B. F. Mertens and C. A. Owen, Jr., entitled "Automated Technique for Recording Time, Intensity and Pattern of Bleeding", in the American Journal of Clinical Pathology, Vol. 55, 1971, pp. 541-550. It has been found, however, that some practice with the device was required in order to obtain reproducible results. This requirement for practice may be traceable to inaccuracies due to the recoil and rebound transmitted to the lancet holder on triggering of the spring lancet. With this known device the skill of the technician is therefore still a vital factor in creating wounds of a predetermined standardized size.
These conditions are analagous to a shot fired from a pistol, which requires a great deal of practice before the person holding the pistol learns to compensate accurately for recoil. Air power pistols are known, however, which have mass and motion compensation to minimize recoil. See, for example, the book Waffenlexikon fuer Jaeqer und Schuetzen (Lexicon of Weapons for Hunters and Sharpshooters) by W. Lampel and R. Mahrholdt, published by F. C. Mayer-Verlag in Muenchen-Solln, 1963, 5th ed., page 83. In weapons of this sort, impact rebound and recoil are compensated by forces of opposition provided by cylinders of equal weight.